1. Field of the Invention
The invention relates to the field of conversion of data from one format to another within a digital data processing device or devices.
2. Background of the Invention
XML (“Extensible Markup Language”) is a proposed standard for exchanging semi-structured data. It can be used as an alternative to HTML. More information about XML can be found in “Extensible Markup Language (XML) 1.0: W3C Recommendation 10 Feb. 1998” http://www.w3.org/TR/REC-xml and in E. H. Harold, XML Extensible Markup Language, (IDG Books 1998).
It is expected that the consumption of XML documents will continue to grow. Business entities increasingly exchange XML documents as part of their business logic flow. Several technical and business organizations have published XML schemes for key document types in specific domains. Web sites such as www.xml.org have been established to coordinate such activities and maintain XML schemes. Existing and new applications also increasingly use XML as their input and output format. Major software vendors, such as those of browsers and relational and object databases, have either provided or announced support for the XML format, while many applications are being enhanced with XML capabilities. If data must be taken manually from other data sources, and integrated into XML documents, then data exchange is slowed.
In A. Deutsch et al, “Storing Semistructured Data with STORED”, SIGMOD '99, International Conf. Management of Data, Philadelphia, Pa. (ACM 1999), pp. 431-442 a language is proposed for mapping data from relational databases to XML. This technique has the disadvantage that, since it uses relational query constructs directly in the mapping language, it can apply only to relational databases.